This application claims the priority of German Application No. 198 55 536.9 filed Dec. 2, 1998, which is incorporated herein by reference.
This invention relates to a spin-stabilized artillery projectile having a driving guide band for imparting a spin to the projectile and a sealing ring mounted on the projectile rearwardly of the driving band.
An artillery projectile of the above-outlined type is described, for example, in German Patent No. 40 00 167 to which corresponds U.S. Pat. No. 5,081,931. The known projectile has a driving band provided with a plurality of circumferential grooves and further has a plastic sealing ring (obturator ring) arranged rearwardly of the driving band. The sealing ring serves for improving the seal of the projectile against the high-pressure propelling gases and is, as a rule, secured to the projectile by shrink-fitting.
It has been bound to be a disadvantage of the above-outlined conventional projectiles that the plastic sealing ring may be easily damaged or destroyed by mechanical effects. Damaged or loosely sitting sealing rings are readily stripped from the projectile upon its loading which may lead to safety-relevant problems for the entire weapon system. Further, it has been found that the sealing rings are often lost during transport of the ammunition because their bias diminishes or disappears as the plastic material of the sealing ring ages.
The known projectiles having a plastic sealing ring arranged rearwardly of the guide band are not adapted for use in up-to-date large caliber weapons (such as tank howitzers) operating with an automated ammunition flow.
It is an object of the invention to provide an improved spin-stabilized artillery projectile of the above-outlined type in which a damaging or destruction or a stripping of the sealing ring upon introduction of the projectile in the loading chamber of the weapon is securely prevented while its sealing function is fully maintained.
This object and others to become apparent as the specification progresses, are accomplished by the invention, according to which, briefly stated, the spin-stabilized projectile includes a projectile body having a longitudinal axis, a forward and a rearward direction; a metal driving band mounted on the projectile body for transferring spinning forces to the projectile body; a circumferential groove provided in the outer surface of the projectile body rearwardly of the metal driving band; and a metal sealing ring seated in the groove and being freely rotatable relative to the projectile body.
Essentially, the invention is based on the principle to provide a metal (preferably copper) sealing ring instead of a plastic sealing ring and the metal sealing ring is seated in a circumferential groove provided in the projectile surface and may freely rotate relative to the projectile.
The metal seal according to the invention does not absorb any energy as the projectile passes through the weapon barrel and since no lateral surface pressure is applied, no wear on the rifling profile occurs, whereby a reliable seal against the propellant gases is ensured.
The seal which is significantly improved as compared to known projectiles to prevent the escape of gas also provides for a significant reduction in the weapon barrel erosion and thus results in a prolongation of the service life of the weapon barrel.
The sealing ring material may be the same as the material used for the driving band; in practice particularly copper/zinc alloys (for example, CuZn10) have been found advantageous.
According to a preferred embodiment of the invention, the groove for the sealing ring has a dovetail cross section; this ensures that even at high projectile rpm""s a lift-off of the sealing ring from the groove is securely prevented.
Existing projectiles which are not adapted for use in weapon systems operating with automated ammunition flow because of plastic sealing rings disposed rearwardly of the guide band may be retrofitted in a simple manner. For this purpose it is merely required to machine a groove into the surface of the projectile rearwardly of the driving band and to press the metal sealing ring into the groove.